The reported issue “RadialTreeLayout throws InvalidOperationException
when Layout having Single Node (Root Node) without Connectors and Child Nodes"
is confirmed as a defect and we have logged an issue report to fix this. This
fix will be available in any of our future releases.

RootNode: A node that does not have any parent is a
RootNode, if there are more than one such node, the first occurrence of such
node is taken as root node in Nodes collection.

Cause of the issue:

The LayoutRoot property does not have any effect in the
Layout because it is overridden by identifying RootNode of the Layout internally.
This is known issue in Layout. We will provide the support to LayoutRoot for
Automatic Layout in our future releases.

We can reproduce the reported issue “Radial TreeLayout
throws InvalidOperationException” only when the RootNode (Explained above)
does not have child Nodes.

If
our scenario (“RootNode does not have child Nodes”) does not math with yours,
please give us more details such as Screenshot, simple sample to reproduce the
reported issue. So that, we would be able to investigate further on this and
update you with appropriate solution.